John Baymore on tue 9 oct 01
Roy, I am not a production potter and therefore am most interested in how=
a glaze looks. .That is not to say that I use obviously unsafe glazes. I
have tried glazes submitted to Clayart as written originally and after
they have been altered to be " food safe.". The original recipes are mo=
re
appealing to me than the altered glazes.Some of the alterations rob the
glaze of its uniqueness.
Mia,
I think you have Ron Roy's family and given names reversed . Unless y=
ou
actually wanted to use his last name as the form of address there. Maybe=
something like "Roy-sensei" or "Roy-sama" works better....... taking the
Japanese approach to names and honorifics .
Unfortunately...... some of the characteristics that make certain glazes
"unique" and "appealing" are directly attributable to the fact that as
stable glasses........ they ain't . For example, oversupply of certai=
n
oxides can cause the percipitation of surface crystals that provide a rea=
dy
source of leachable materials to foods, or allow the action of acid rain =
to
change the appearance of a tile fascade or a piece of sculpture. Those
surface crystals are what gived the glaze all it's "punch". Take them aw=
ay
to stabilize the leaching issue.... and you take away all the "character"=
. =
Which is a REAL pain in the butt. Sometimes it seem that the more "kille=
r"
the glaze........ the worse the glass. =
Sometimes.... ignorance is bliss. Raw lead glazes are so gorgeous. When=
we didn't know so much about lead.... we could use all those gorgeous
recipes and not think a thing of it. Now we are kinda' stuck HAVING to
think about it. Wish we COULD just ignore it .
In a venue like CLAYART open and involved discussion of these types of
issues is VERY important....... because there are so many people reading
the postings who have little real technical background. For many, CLAYAR=
T
is their major resource for ceramics technical information.....since they=
don't have professors or mentors to go to, or their sources themselves ar=
e
weak in these areas. Ron would be sort of remiss NOT to point out the
possible instability of such a glaze, so that those reading the postings=
at least have the chance to gather more information. Many of us feel sor=
t
of an "obligation" to the professional community here to "jump in" in
certain topic areas.
Carleton Balls' glazes, ( I have dozens of them from CM when Professor
Ball had a monthly column)are generally very dependable glazes. Westwood
Ceramics, later Laguna, sells some of his glazes. Particularly Transparen=
t
16, MG 2 Matt, G Matt 3.just to mention a few. The last glaze. can resu=
lt
in some wonderful effects.
As John Hessleberth has repeatedlly noted here on CLAYART and at NCECA, t=
he
fact that a glaze is in wide distribution, or that it is supplied by
commercial manufacturer is no guarantee that it is actually a stable glaz=
e.
No one is (YET) regulating this area other than for lead and cadmium
release.
As I pointed out at my NCECA presentation in 99, just because "Mr./ Ms Bi=
g
Name" ceramic artist is well known and recognized as a maker of wonderful=
objects....... does not necessarily mean that person has much in the way =
of
real technical understanding about clay and glaze formulation. Some of t=
he
recipes that you will see "out there" that are coming from such a source
are not really all that stable. Too few schools include a strong technic=
al
curriculum requirement when they grant their BFA and MFA degrees........ =
so
many well known ceramic artists get little real education in this area. =
In
my survey in 99, it was clear that few schools even presented molecular
glaze calculation in their required curriculum structure. Hopefully this=
is changing or will change.
Professor Carlton Ball certainly was a "glaze guru " for the time in whic=
h
he was a major force in the glaze world and writing his columns. Time an=
d
life has moved on and we know a lot more now than we did then. I am
confident that that if he were still writing such materials.... Professor=
Ball would be right in there with Ron R. and John H. looking at this very=
subject and cutting some new ground right along with them.
As of right now..... John Hessleberth and Ron Roy are THE authorities on
the subject of glaze stability, outside maybe a few the "industrial world=
".
They are breaking important ground for us.... and ground breakers often
are looked at as "bearers of bad news". We all need to be careful that w=
e
don't "shoot the messenger" for the news they bring .
As we all know, there are countless books and mags that have formulas for=
glazes containing lead bearing compounds. Lead is a SUPER material for
making reliable, beautiful glazes ..... if you ignore all the toxicity
issues. At one time, until even pretty recently, potters thought nothin=
g
of using such formulations on their wares. As we have gained knowledge
about the "workings of the world" we have learned that it is difficult to=
utilize Pb compounds in a manner that is safe for either the potter, the
user, or both. So other than in very specailized applications.... mostly=
in industry where they have the controls necessary, their use has fallen
out of favor and is actually regulated by the government.
As we learn even more about our glazes...... we will likely find that oth=
er
"old standby" practices that we have used will reveal their flaws under
tighter scrutiny.
"Dependable" is a term that begs the question "How are you determining th=
is
quality"?
Dependable from most potter's USUAL point of view involves things like
reliability in application, tolerance to firing variations, free from
obvious easily seen defects such as crawling and pinholoing, and so on. =
Potters tend to take a "macro" point of view...... if it looks like a
glaze, smells like a glaze, and feels like a glaze...... it's a glaze. =
What is just starting to happen is that some potters are beginning to tak=
e
a more "micro" level view of something that they never really considered
much..... the invisible world of the chemistry and physical properties of=
the glazes. We are discovering that all may not be as it first appears.
It's fairly new ground for the "artist potter"..... although industry has=
been a bit ahead of us in this regard.....being a bit more scientific in
approach in general.
The ready availability of wonderful comprehensive glaze chemistry softwar=
e
like "Insight" (thanks, Tony ) has allowed us to easily learn more abo=
ut
this chemical viewpoint of glazes, the conceptual basis for which has bee=
n
around for a very LONG time (thanks Hermann ).
All this takes some getting used to, particularly for the "old dogs" like=
me . Some of what we learn we won't like.
The State of California has very stringent laws about glaze safety. If
there was a question about them they would not be
sold nor used by many potters.
The State of California has very stringent laws only about lead and cadmi=
um
release from ceramic glazes. CA's laws are more restrictive than the USF=
DA
ones. To my knowledge, as of yet.... they, and the FDA, do not regulate
the leaching of any other compounds. Unless something is very new on the=
books (and there might be), CA doesn't look at GENERAL glaze safety. =
California effectively followed the federal government's lead in looking =
at
the Pb and Cd issue......... but simply set standards that are more
restrictive.
It is my opinion that it is only a matter of time before the leaching of
other materials from glazes gets scrtutinized by regulatory bodies. It m=
ay
be California that takes the lead.... or it may be the USFDA. All the op=
en
discussion of the topic here on CLAYART, in mags like CM and Clay Times, =
and at places like NCECA makes this all the more likely to happen. We ar=
e
beginning to police ourselves a bit at this point...... but the formal
regulatory bodies will likely still take a look eventually.
The laws of merchantability and the liability statutes in all states appl=
y
to possible harm caused by any material leaching out of a glaze whether
there is a specific glaze leaching law or not. If your product harms
someone, and proof can be established, then you might have a problem on
your hands. Similarly if you take a public commission for a tilework
building fascade... and the pigeon poop and acid rain cause it to
dramatically deteriorate in very short order.......... the laws of
merchantability might have you redoing the whole installation.
Glaze stability and durability is not just an issue for the so-called
"production potter". It could apply to sculptors and tile makers too.
There was a letter to Clayart within the last few days,from someone who
analyzed MG2 and said that it would not craze, and was therefore durable.=
Crazing is not the ONLY measure of "durability", which itself is a somewh=
at
subjective term. =
You'll find posts to CLAYART that say all sorts of things,............
including the weird ramblings I tend to post . Some writers are bette=
r
sources of information than others. On the subject of glazes, there is
just about no one with a better grasp of the technical side of the field
than "Roy-sensei".
Best,
..............................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752 (s)
800-900-1110 (s)
JohnBaymore.com
JBaymore@compuserve.com
John.Baymore@GSD-CO.com
"Earth, Water, and Fire Noborigama Woodfiring Workshop 2002 Dates TBA"=
Ron Roy on fri 12 oct 01
Hi John,
If what you post are weird ramblings - we can use more of that.
Thanks John for saying all that so well - your understanding of these
issues is a constant encouragement to those of us who are trying to do
something about them.
Now what do I do about my burning ears?
RR
John Baymore said
>You'll find posts to CLAYART that say all sorts of things,............
>including the weird ramblings I tend to post . Some writers are better
>sources of information than others. On the subject of glazes, there is
>just about no one with a better grasp of the technical side of the field
>than "Roy-sensei".
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
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